[TIL] 20201126 JavaScript Strings and More

String

• Represents text
• Must be wrapped in quotes, either double or single.
• Warning : 23 ≠ '23'

let username = "Jiwan";
let username = 'Jiwan';

let username = 'Jiwan"; //error

 

 

String Index

• Strings are indexed. Each character has a corresponding index (positional number)
• Index starts at 0.

 

 

String Length

• Length of index.
• (Index of last letter) + 1 = Length

 

 

String Concatenation

• Put multiple strings or non-string types together.
• "String1" + "String2" = "String1String2"
• 1 + "String" = "1String"

 

 

String Method

• Built-in actions we can perform with individual strings.
• String methods are used when
  • Searching within a string
  • Replacing part of a string
  • Changing the casing of a string
• Syntax 
  
  • something.method();
• examples
  • toUpperCase()
  • toLowerCase()
  • trim()

 

 

String Methods with Arguments

• Argument
  • Inputs that some methods accept inside of parentheses.
  • Syntax : something.method(arg)
  • examples
    • indexOf()

'catdog'.indexOf('cat'); //0
'catdog'.indexOf('z'); //-1 (not found)

 

 

 

String Template Literals

• Strings that allow embedded expressions, which will be evaluated and then turned into a resulting strings.
• Back-ticks( ` ) are used, not single quotes.
• Syntax : `String ${expression} String`

 

 

Undefined & Null

• Null 
  • Intentional absence of any value.
  • Must be assigned.
• Undefined
  • Variables that do not have an assigned value are undefined.

 

 

Random Numbers & The Math Object

• Math Object
  • Contains properties and methods for mathematical constants and functions.
  • Methods
    • Math.round() : Rounding a number. 
    • Math.abs() : Absolute value
    • Math.pow(x,y) : Raises x to the yth power
    • Math.floor() : Removes decimal

Math.round(4.9); //5
Math.abs(-3); //3
Math.pow(2,5); //32
Math.fllor(3.8); //3

 

• Random Number
  • Gives a random decimal between 0 and 1 (non-inclusive: doesn't include 1)
  • Math.random();

 

 

 

 

 

* This post is a summary of Udemy Course "The Web Developer Bootcamp" by Colt Steele.